A file’s hash value is a signature for that file that uniquely identifies it. If a file’s contents change, its hash value will also change. You can use the hash value of a file to know whether it has been modified or altered. You can also cross-check the hashes of a suspicious file online to see if it’s a malicious file. Windows 7 does not have any native way to show or calculate a file’s hashes. But you can use the freeware HashTab tool to add a File Hashes tab in the file properties dialog.